The present invention concerns capacitors, particularly flat aluminum electrolytic capacitors used in medical devices, such as implantable defibrillators, cardioverters, and pacemakers.
Since the early 1980s, thousands of patients prone to irregular and sometimes life threatening heart rhythms have had miniature defibrillators and cardioverters implanted in their bodies, typically in the upper chest area above their hearts. These devices detect onset of abnormal heart rhythms and automatically apply corrective electrical therapy, specifically one or more bursts of electric current, to hearts. When the bursts of electric current are properly sized and timed, they restore normal heart function without human intervention, sparing patients considerable discomfort and often saving their lives.
The defibrillator or cardioverter includes a set of electrical leads, which extend from a sealed housing into the walls of a heart after implantation. Within the housing are a battery for supplying power, monitoring circuitry for detecting abnormal heart rhythms, and a capacitor for delivering bursts of electric current through the leads to the heart.
In many instances, the capacitor takes the form of a flat aluminum electrolytic capacitor. This type of capacitor generally includes a stack of flat capacitor elements, with each element including one or more paper separators between two sheets of aluminum foil. One of the foils serves as the anode of the capacitor element, and the other serves as the cathode. Each anode foil in the stack, and each cathode foil in the stack, is interconnected to the other anodes and cathodes respectively. Connecting the anodes and cathodes provides a total capacitance equal to the sum of the capacitances of all the capacitor elements. After being connected, the respective anodes and cathodes are connected to terminals for being coupled to circuitry outside the capacitor case.
Since defibrillators and cardioverters are typically implanted in the left region of the chest or in the abdomen, a smaller size device, which is still capable of delivering the required level of electrical energy, is desirable.
Accordingly, there is a need to provide a compact capacitor capable of providing the required pulse of energy for use within the device. Furthermore, there is a need to provide methods of manufacturing a capacitor and structures within the capacitor that provide greater process control, less expensive manufacturing, and provide for a design efficiently utilizing space within the capacitor case.
To address these and other needs, various capacitor structures and methods of manufacturing have been devised.
One aspect of the present invention provides a capacitor having one or more anodes and a cathode structure comprising a plurality of integrally connected cathode plates, the cathode structure having a serpentine shape, interweaving under and over each of the one or more anodes, wherein each of the one or more anodes is located between a pair of adjacent cathode plates.
One aspect provides a feedthrough assembly having an electrically conductive member dimensioned to extend at least partially through a feedthrough hole of a case of the capacitor, the conductive member having a passage therethrough. In one embodiment, the passage includes a threaded section.
One aspect provides a capacitor having a first stack of capacitive elements where each element comprises an anode plate and a cathode plate with an electrolyte interposed therebetween and a second stack of capacitive elements, wherein the first and second stacks are enclosed in separate compartments of a capacitor case that electrically isolate the electrolytes of each stack from one another.
One aspect provides a capacitor case including a portion having opposing interior and exterior surfaces, with the portion having a hole; and a semi-permeable membrane adjacent the hole to regulate passage of fluids through the hole.
One aspect provides a capacitor having a first anode stack having a different number of anode foils than a second anode stack. A first connection member is attached to the first anode stack, the first connection member having a first section extending over and confronting an edge face of the first anode stack. A second connection member is attached to the second anode stack, the second connection member having a first section extending over and confronting an edge face of the second anode stack, wherein the first connection member and the second connection member are connected to each other and wherein the first section of the first connection member is a different size than the first section of the second connection member.
One aspect provides a capacitor having a case having a curved interior surface, and first, second, and third capacitor modules, each having an anode stack and a cathode and each having respective first, second, and third edge faces that confront the curved interior surface of the case, with the third edge face set back from the second edge face and the second edge face set back from the first edge face to define a profile generally congruent to a profile of the curved interior surface, wherein the first capacitor module anode stack having a first number of anode foils and the second capacitor module anode stack having a second number of anode foils, where the first number of anode foils is different than the second number of anode foils.
Another aspect of the present invention includes various implantable medical devices, such as pacemakers, defibrillators, and cardioverters, incorporating one or more capacitors having one or more of the novel features described above.